Can we stop the distally migrating mandibular second premolar?

Published: July 2016

Bulletin #57, July 2016

Can we stop the distally
migrating mandibular second premolar?

A definite distal angulation of the
developing tooth bud of the mandibular second premolar has received relatively
little attention in the orthodontic literature. Nevertheless it seems to be a
trait that occurs with some regularity and, in its most extreme expression, has
serious implications for its own future. It additionally may become a factor
that challenges the future of adjacent teeth and occlusal function.

In an earlier bulletin on this website,1 I noted that the
tooth may be found with its occlusal surface jammed against the mesial root,
usually close to the CEJ, of the first molar. Sometimes it may more
horizontally orientated and well down at the level of the mucosa of the floor
of the mouth and located lingual to the molar roots. In either of these two
cases, molar root resorption may occur in the premolar contact area with the
molar root. It was also pointed out there that the second premolar is often
late in its development and, aside from the third molars, is the most likely tooth
to be congenitally missing. An association has been found between the distally
tipped premolar, late-developing second premolars, late-developing dentitions,
infraoccluded deciduous predecessors and the incidence of palatal canines.2-6

The aim of that bulletin was to
describe a method of treatment in which the tooth is first brought occlusally
simultaneously with a lingual directional component, in order to draw it clear
of the roots and broad lingual bulge of the crown of the molar. Once the
impaction of the tooth is resolved in this manner, it is drawn mesially and
buccally into its place in the arch.

My purpose in this month’s bulletin
is to illustrate the natural history of the development of this uncommon anomaly
in a specific case and to discuss whether anything could have been done to
avoid these damaging consequences.

The Patient

Fig. 1. Panoramic view of a 9 year old male patient, taken
in 2009, showing an unusually early mixed dentition with only first permanent
molars and 4 mandibular incisors erupted. With the exception of the mandibular
first primary molars and left primary deciduous canine, all deciduous teeth were
in place. The clinical examination revealed severe caries experience, with
untreated cavities present. All the permanent teeth could be identified on the
radiograph, although the dental age of the patient was assessed as 6-7 years.
Space loss was noted following the extraction of the deciduous first molars.
The second premolar tooth germs could be seen to be rotated distally at almost
90 degrees and their state of calcification was assessed as corresponding to a
dental age 4-5 years.

Figure 1 is the panoramic film of a
7.5 year old male in the early mixed dentition stage, taken in 2009. He already
has considerable caries experience, having already lost the two mandibular
first deciduous molars and displaying active caries in the other deciduous
molars. The apices of the erupted mandibular permanent incisors and first
permanent molars are open and there is still some development of these roots to
be expected over the next year or two.

While the overall dental age of
this patient is a year or so late, in relation to his chronologic age, the
mandibular second premolars are markedly retarded by as much as 2-3 years
behind their expected development, at this dental age. Calcification of the
crowns of these teeth still has more than a year to go before their completion
and before root development begins. Secondly, both these teeth are 900
rotated distally within their respective crypts and displaying a horizontal
orientation.

Fig. 2. The patient in 2011. The maxillary incisors have
erupted, the mandibular canine and first premolars appear to be vying for the
already reduced space which is being stabilized by a fixed lingual arch. The
maxillary canines a very high in close proximity to the apices of the lateral
incisors. Both second premolars appear to have uprighted to a degree.

In figure 2, taken 2 years later, a
lingual arch space maintainer is evident, the maxillary incisors have erupted
and some restorative treatment has been performed. The orientation of the
second premolars has noticeably improved by 25-300with the calcification of the crowns nearing
completion. Shortly after this film was taken, the practitioner extracted the
mandibular second deciduous molars, in the hope that this would further influence
the premolars to favorably and spontaneously change their eruptive path.

Fig. 3. In 2013, with the patient now 13 years of age, only
the maxillary primary second molars remain. The second mandibular primary
molars had been extracted some time earlier and the erupted first premolars
have tipped distally to a considerable. The second premolars are clearly
visible in line with the mesial aspect of the first permanent molars, which are
themselves noticeably tipped mesially.

Figure 3 was taken 2 years later
and shows erupted premolars and canines with appropriate root development, although
the first premolars have also drifted distally into close relation to the first
permanent molars. At the same time, the second premolars still show less than a
quarter of their final expected root length. Concurrently, these teeth have slightly
worsened the angle of their orientation and some space has been lost in the
erupted dental arch, despite the presence of the space maintainer.

Fig. 4.In the space
of a further 3 years, this 16 year old male has a fully erupted dentition,
aside from the second premolars, which have now completely by-passed the roots
of the first molars and on the right side is in line with the mesial aspect of
the root of the second molar.

The final panoramic view (Fig. 4),
taken 2.7 years later, shows a slightly worsened orientation of the premolars,
but a strong distal migrational movement on both sides, to bring the occlusal
surfaces of these teeth to beyond the distal aspect of the first molars and
almost in a line with the mesial aspect of the erupted second permanent molars.
To date, no orthodontic intervention has been undertaken.

Discussion

Following are a series of questions
and answers relating to various forms of early interceptive therapy that were
performed and others that might have been considered. As one may imagine the
answers to these questions are highly subjective and, when attempting to set
down guidelines, it is emphasized that each individual case must be judged on
its merits in relation to the myriad of aspects that are involved, from
objective dental development issues through susceptibility to caries, to
patient management problems. As such, none of these answers will be supported
by solid evidence-based data, but will be buttressed by a healthy clinical bias
based on my own 55 years of clinical experience, highly influenced by that of
the collected wisdom of several of my closest colleagues.

Question: Was the decision to extract the second
deciduous molars at that time a logical step?

Answer: There is no evidence that extraction of the
deciduous second molar could de-rotate the second premolar tooth buds in their
follicles. Furthermore, by extracting these teeth, any minor restraint to
distal drifting that could be expected from the short-term continued presence
of the distal root of the deciduous tooth, was removed.

Question: If the rapid distal tipping of the first
premolar that occurred following the extraction of the second deciduous molar
had been prevented by modifying the space maintainer or had been subsequently
corrected by the addition of a few orthodontic brackets and a coil spring, to
create space, would that have influenced the second premolar to improve its
eruption path?

Answer: This, too, is most unlikely, although it
cannot be ruled out altogether.

Question: Could early orthodontic treatment to tip the
first molars distally, with correction of the first premolar, have positively
influenced the outcome?

Answer: This option does offer hope of some limited
self-correction but, again, the chances are still not high.

Question: At what stage would it have been
advantageous to have exposed, attachment bonded and applied traction?

Answer: In general, the best time to expose an
impacted tooth is when 2/3 of its potential root length has developed, since
this is the time when a permanent tooth normally erupts autonomously. If the
tooth were to be exposed when a third or less of the root is calcified, there
is a significant chance that the surgical procedure will result in damage to
the tooth germ and may lead to premature root closure and shorter-than-normal
root length.On the other hand, this may
turn out to be the lesser of the two evils, since the tooth will be much more
accessible and provide an improved chance of orthodontic treatment success.
Unfortunately, the rapid distal drift appears to gather momentum well before
the root development has proceeded to the desired root length.

Question: Clearly, the orientation of the crown of the
tooth dictates its eruption path. That being so, would surgical exposure and
manipulative rotation of the follicle incorporating the tooth bud be an
appropriate procedure?

Answer: We have done this on one or two occasions, but
our follow-up has not been adequate and our experience is lacking. Can we
conclude that all was well? Obviously not. However, in much the same way that
the autogenous transference of an immature tooth can be successfully implanted
from its original developmental site to the prepared socket in an edentulous
area, there may be a good argument for using this procedure in the present
context. These rotated second premolar teeth frequently display very late
development and root development may not have commenced. However, the more the
root has developed, the less the practicability of turning the tooth through
70-90 degrees.

Question: Is the present location of the errant
premolars treatable in the manner described in the February 2012 bulletin or is
the situation now beyond what is amenable to orthodontic treatment?

Answer: When a second premolar has migrated further
distally than the distal root of the molar, technically it can still be drawn
to its place. However, it is difficult in these circumstances to draw it
mesially and superiorly while ensuring that it remains within the confines of
the alveolar bone and to avoid fenestratingthe tooth through the lingual plate of the mandible. In this
eventuality, the tooth could undoubtedly be brought into its place in the
dental arch, but its lingual side would be devoid of its bony socket wall on
the lingual side and its attendant prognosis would be compromised.

Question: If we extract these errant premolars, is
orthodontic space closure a good alternative treatment plan or perhaps we
should simply hold the space for later implant placement?

Answer: This must depend on the dental and skeletal
relations of the patient and the plan for the orthodontic treatment of the
malocclusion as a whole. In an extraction case, space closure would obviously
be a factor to be considered. In the case illustrated here, the second
deciduous molar had been extracted fairly early on and, in the absence of the
premolar, the form of the ridge will be adversely affected by resorption over
the long period of time that must elapse before this child will be ready for
implants. Orthodontic space closure in a non-extraction case would best be
approached with the use of temporary anchorage devices in preference to dental
anchorage, while monitoring eruption of the third molars (Fig. 4).

References

1.Seehttp://dr-adrianbecker.com/page.php?pageId=281&nlid=26 February 2012 bulletin #8 on this website